Metal foams have been produced by melt processing, powder processing, deposition techniques, and other methods [1]. Melt processed foams are formed by using either a blowing agent such as a metal hydride, metal carbide, or metal oxide, or by using a lost-polymer investment casting. Metal foams produced using blowing agents often have an inhomogeneous cell structure and density that is due to the non-uniform distribution of blowing agent in the melt. These foams also tend to have a closed cell structure, which limits their uses to structural applications. Open celled foams are preferred for applications related to, for example, catalysis and heat transfer, because the open cell structure allows for the passage of fluid (gas, liquid) through the foam.
Nanostructured metals monoliths have been prepared using polymer or aerogel templates, electrodeposition, and etching of noble metal alloys [5,7]. Metal monoliths prepared by these methods are typically in the form of powders and thin films, and almost all of these methods require template removal to access the nanoporous metal.
The production of porous monolithic structures without using a template continues to be a challenge. Additional challenges are related to controlling the cell structure and shape of the porous monolith, which will likely have an impact on applications such as catalysis, electrode design, and sensor applications. Understanding the factors that control pore sizes in porous metal monoliths could be used in the rational design of nanoporous metals. Furthermore, the lack of generality and flexibility of the current methods in the preparation of nanoporous materials with a variety of different metals remains a problem. The ability to prepare a variety of different nanoporous metals would significantly expand the range and utility of porous metals.
Accordingly, an object of the present invention is a method for preparing porous metal.
Another object of the present invention is to provide materials that can be transformed into porous metal.
Yet another object of the present invention is to provide a general method for preparing nanoporous metal monoliths.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.